(Sep 11, 2010)

At it's core, the study of mortality is based on a simple ratio -
the number of deaths, D, divided by the population exposed to the
risk of death, E:

mortality rate = D / E

While this seems simple and straightforward, there are important
subtleties concerning the quality of the data used. One of these is
illustrated by a series of revelations about unreported
deaths in Japan, where a recent audit has cast doubt on the reliability
of Japanese population statistics for the elderly. Unreported deaths
reduce mortality rates both by under-counting deaths and by inflating the
population at risk. Time will tell if Japan's famously low mortality
rates have been under-stated as a result.